Pneumatic booster

Abstract

There is provided a pneumatic booster, comprising: a front shell; a rear shell; a housing formed as that respective openings of the front shell and the rear shell are integrally connected to each other, and a power piston arranged in the housing so as to divide an interior of the housing into a constant-pressure chamber on the front shell side and a working-pressure chamber on the rear shell side, wherein thrust force of the power piston generated by pressure difference between the constant-pressure chamber and the working-pressure chamber is applied to inputted force transmitted from a brake pedal to an input rod so as to obtain combined force, the combined force being outputted with a given boost ratio from an output rod, and wherein a thickness of the front shell is made to be thinner than a thickness of the rear shell.

What is claimed is: 
     
       1. A pneumatic booster, comprising:
 a front shell being mostly configured to have a single piece of material; 
 a rear shell being mostly configured to have a single piece of material; 
 a housing formed of the single piece material of the front shell and the single piece material of the rear shell integrally united to each other at respective openings, and 
 a power piston arranged in the housing so as to divide an interior of the housing into a constant-pressure chamber on the single piece material of the front shell side and a working-pressure chamber on the single piece material of the rear shell side, 
 wherein thrust force of the power piston generated by pressure difference between the constant-pressure chamber and the working-pressure chamber is added to inputted force transmitted from a brake pedal to an input rod so as to obtain combined force, the combined force being outputted with a given boost ratio to an output rod, and 
 wherein a thickness of the single piece material of the front shell is made to be thinner than a thickness of the single piece material of the rear shell, and 
 a tie rod is arranged by penetration of the power piston so as to unite the single piece material of the front shell with the single piece material of the rear shell, the tie rod being provided with a mounting screw portion to a vehicle body on one end side thereof. 
 
     
     
       2. The pneumatic booster according to  claim 1 , wherein the difference between the thickness of the single piece material of the front shell and the thickness of the single piece material of the rear shell is defined within 0.1 mm to 0.3 mm. 
     
     
       3. The pneumatic booster according to  claim 1 , wherein a fixed screw portion is provided on the other end side of the tie rod for fixation of a master cylinder. 
     
     
       4. The pneumatic booster according to  claim 1 , wherein the single piece material of the rear shell comprising:
 a cylindrical portion where a valve body is inserted, the valve body movable within the housing; 
 a vehicle attached portion provided on an outer periphery of the cylindrical portion, the vehicle attached portion being attached to a vehicle body when mounting on the vehicle body; 
 a major-diameter cylindrical portion being united to the single piece material of the front shell; and 
 an inclined portion, formed approximately into circular cone, connecting the major-diameter cylindrical portion with the vehicle attached portion, 
 wherein the inclined portion is provided with a plurality of bent portions in a radial direction of the rear shell, each of the plurality of bent portions extending circumferentially as a part of the rear surface of the rear shell. 
 
     
     
       5. The pneumatic booster according to  claim 1 , wherein the single piece material of the front shell and the single piece material of the rear shell are united to each other by caulking a periphery of the single piece material of the front shell. 
     
     
       6. The pneumatic booster according to  claim 1 , wherein the constant-pressure chamber is configured to have a connection to a negative pressure source; an internal pressure of the working-pressure chamber is configured to be changed due to either a connection to the constant-pressure chamber or access to atmosphere, and the thickness of the single piece material of the rear shell is set to be the one which enables to suppress deformation by pressure fluctuation of the working-pressure chamber at braking. 
     
     
       7. A pneumatic booster, comprising:
 a front shell on which a master cylinder is mounted, the front shell being mostly configured to have a single piece of material; 
 a rear shell being mostly configured to have a single piece of material and being arranged on a side of a vehicle body; 
 a housing formed of the single piece material of the front shell and the single piece material of the rear shell integrally united to each other at respective openings; 
 a power piston arranged in the housing so as to divide an interior of the housing into a constant-pressure chamber on the single piece material of the front shell side and a working-pressure chamber on the single piece material of the rear shell side; and 
 a tie rod that penetrates the single piece material of the front shell, the single piece material of the rear shell and the power piston, the tie rod being provided with a mounting screw portion to the side of a vehicle body on one side of the tie bar, 
 wherein thrust force of the power piston generated by pressure difference between the constant-pressure chamber and the working-pressure chamber is added to inputted force transmitted from a brake pedal to an input rod so as to obtain combined force, the combined force being outputted with a given boost ratio to an output rod, and 
 wherein a thickness of the single piece material of the front shell is made to be thinner than a thickness of the single piece material of the rear shell. 
 
     
     
       8. The pneumatic booster according to  claim 7 , wherein the difference between the thickness of the single piece material of the front shell and the thickness of the single piece material of the rear shell is defined within 0.1 mm to 0.3 mm. 
     
     
       9. The pneumatic booster according to  claim 7 , wherein a fixed screw portion is provided on the other end side of the tie rod for fixation of the master cylinder. 
     
     
       10. The pneumatic booster according to  claim 7 , wherein the single piece material of the rear shell comprising:
 a cylindrical portion where a valve body is inserted, the valve body movable within the housing; 
 a vehicle attached portion provided on an outer periphery of the cylindrical portion, the vehicle attached portion being attached to the vehicle body when mounting on the vehicle body; 
 a major-diameter cylindrical portion being united to the single piece material of the front shell; and 
 an inclined portion, formed approximately into circular cone, connecting the major-diameter cylindrical portion with the vehicle attached portion, 
 wherein the inclined portion is provided with a plurality of bent portions in a radial direction of the rear shell, each of the plurality of bent portions extending circumferentially as a part of the rear surface of the rear shell. 
 
     
     
       11. The pneumatic booster according to  claim 7 , wherein the single piece material of the front shell and the single piece material of the rear shell are united to each other by caulking a periphery of the single piece material of the front shell. 
     
     
       12. The pneumatic booster according to  claim 7 , wherein the constant-pressure chamber is configured to have a connection to a negative pressure source; an internal pressure of the working-pressure chamber is configured to be changed due to either a connection to the constant-pressure chamber or access to atmosphere, and the thickness of the single piece material of the rear shell is set to be the one which enables to suppress deformation by pressure fluctuation of the working-pressure chamber at braking. 
     
     
       13. A pneumatic booster, comprising:
 a front shell on which a master cylinder is mounted, being mostly configured to have a single piece of material; 
 a rear shell being mostly configured to have a single piece of material, and being arranged on a side of a vehicle body; 
 a housing integrally formed of the single piece material of the front shell and the single piece material of the rear shell; 
 a power piston that is arranged in the housing so as to divide an interior of the housing into a constant-pressure chamber on the single piece material of the front shell side and a working-pressure chamber on the single piece material of the rear shell side; 
 a tie rod that penetrates the power piston so as to unite the single piece material of the front shell with the single piece material of the rear shell, the tie rod being provided with a mounting screw portion to the side of a vehicle body on one side of the tie bar and also being provided with a fixed screw portion on the other end side of tie rod for fixation of the master cylinder; 
 a valve body that is movably inserted into the housing so as to connect with the power piston; 
 an input rod that is inserted into the valve body, and that is connected to a brake pedal through a clevis; 
 a plunger that is connected with the input rod, the plunger being movable within the valve body; 
 an output rod that is provided with the valve body so as to operate the master cylinder; 
 a reaction member that is provided between the output rod and the valve body or the plunger, the reaction member partially transmitting reaction force generated from the output rod to the plunger; and 
 a control valve enabling to convert a connection between the working-pressure chamber and atmosphere as well as a connection between the constant-pressure chamber and the working-pressure chamber; 
 wherein a thickness of the single piece material of the front shell is made to be thinner than a thickness of the single piece material of the rear shell, and one end side of the tie rod is fixed to the rear shell through caulking. 
 
     
     
       14. The pneumatic booster according to  claim 13 , wherein the difference between the thickness of the single piece material of the front shell and the thickness of the single piece material of the rear shell is defined within 0.1 mm to 0.3 mm. 
     
     
       15. The pneumatic booster according to  claim 13 , wherein the single piece material of the rear shell comprising:
 a cylindrical portion where a valve body is inserted, the valve body movable within the housing; 
 a vehicle attached portion provided on an outer periphery of the cylindrical portion, the vehicle attached portion being attached to the vehicle body when mounting on the vehicle body; 
 a major-diameter cylindrical portion being united to the single piece material of the front shell; and 
 an inclined portion, formed approximately into circular cone, connecting the major-diameter cylindrical portion with the vehicle attached portion, 
 wherein the inclined portion is provided with a plurality of bent portions in a radial direction of the rear shell, each of the plurality of bent portions extending circumferentially as a part of the rear surface of the rear shell. 
 
     
     
       16. The pneumatic booster according to  claim 13 , wherein the single piece material of the front shell and the single piece material of the rear shell are united to each other by caulking a periphery of the single piece material of the front shell. 
     
     
       17. The pneumatic booster according to  claim 13 , wherein the constant-pressure chamber is configured to have a connection to a negative pressure source; an internal pressure of the working-pressure chamber is configured to be changed due to either a connection to the constant-pressure chamber or access to atmosphere, and the thickness of the single piece material of the rear shell is set to be the one which enables to suppress deformation by pressure fluctuation of the working-pressure chamber at braking.